This invention relates to round manhole cover supports for emplacing over and raising the grade of an existing manhole cover-receiving structure, more particularly to such supports that are adjustable to fit access holes, and especially to such supports that can accomodate a group of circular manhole covers of a standard size and shape where the frames or other existing cover-receiving structures thereunder diverge somewhat as to the diameter of the covers that can fit them.
For simplicity the term "existing manhole cover-receiving structure" is used here to refer to the existing, i.e., fixed in-place frame or other seating receptacle for a removable cover or grating that covers an access hole (i.e., hand hole, tool hole, manhole, catch basin or the like). The term "manhole cover" is used in this application to refer to a round removable cover or grating over the access hole. The resulting assembly of a receiving structure and a manhole cover ordinarily is intended to bear vehicular traffic. The term "manhole cover support" or simply "cover support" here means a structure that fits over the existing manhole cover receiving structure, raises its grade, and thereby accommodates a cover or grating at the new elevated grade. The access hole covered usually is a utility enclosure serving, e.g., an electric, gas, water, sewer or storm drainage system.
The preponderance of manholes are circular (in street plan), have circular covers and have existing cover-receiving structures such as frames that have circular access holes, circular sills to support the cover, and circular lateral cover keepers (the latter also sometimes termed "collars"). Accordingly, this specification is directed to round manhole cover supports that have ring-like annular elements which are to interact with an existing round manhole cover-receiving structure.
Ordinarily a cover support finds its use when a roadway such as a street or highway is resurfaced with an added layer of paving material, typically asphalt concrete or sheet asphalt, to establish a higher grade. A principal use for the instant cover support is expected to be in a municipality where a group of manhole installations of somewhat varying diameters are likely to be encountered in the resurfacing. Thus, adjoining or the same subdivisions, boroughs, wards or districts may have existing manhole cover frames for accommodating a group of covers that are nominally of several fairly close sizes, say, about 23 or 24 inches in diameter. When resurfacing in such an area, it may be decided to standardize on a single diameter, 24- or 25-inch, cover for this group to reduce the inventory of covers, purchase covers in larger lots, avoid having to use or to buy potentially costly custom-built equipment or require short manufacturing runs, and certainly to eliminate the digging out, raising and resetting of the existing frames or other cover-receiving structures simply to accommodate their original variously-sized manhole covers. It then can be especially advantageous to mount the inventive cover supports atop these existing manhole cover frames for the standardization purpose.
Heretofore the typical installation of new manhole cover supports has seemingly been circumscribed by and restricted to the reuse of the old cover. The possible benefits of standardizing on a new, larger cover diameter in place of a group of covers that include ones which vary a little in diameter from one to another or from one subgroup to another, then designing a new cover support expressly for the new standardized covers appears to have gone unrecognized; it does not seem to have been addressed at all by the art other than my prior applications Ser. Nos. 07/323,622 ; and 07/362,277 referred to above.
Axle loads up to 18,182 kg. must be resisted by many of these cover supports as well as serious impact loads from vehicles and snow plows plus a variety of temperature effects, steam leaks, spillage, etc., without permitting a hazardous dislocation of the cover support or its cover. Often it is desirable also to cushion the cover for resisting wear or Reducing noise, and/or to seal the cover and its cover support against a substantial and possibly overloading infiltration of surface water. e.g., storm drainage that otherwise would enter a sanitary sewer system at various manhole locations.
The instant cover support can be made especially highly resistant to displacement and dislodgement in service, i.e., stable. Preferably it incorporates structural or mechanical holddown (anchoring) means to the existing manhole cover-receiving structure, e.g., strong hook-like extensions that are integral with it or are easily attached. Also, it can be constructed to maintain a strong frictional grip in the existing manhole cover-receiving structure. Its unique structure fills a place in street maintenance that has heretofore been neglected.